Method and Device for Locating the Right or Left Position of a Wheel of a Vehicle

ABSTRACT

The invention relates to a method and a device for locating the right or left position of a wheel ( 2 ) of a vehicle ( 3 ). According to the invention, the wheel ( 2 ) is equipped with a magnetic measuring component ( 4 ) comprising a core made of ferromagnetic material on which are arranged, crosswise, two windings designed to present maximum sensitivity axes extending in a plane intersecting the axis of rotation of said wheel, and offset from each other, in this intersecting plane, by a predetermined angle θ, and on movements of the vehicle, a measurement is taken of a signal generated by the variation of a magnetic field at the terminals of each of the windings so as to deliver two periodic signals phase-shifted from each other by (+or −) θ, the direction of rotation of the wheel ( 2 ) is determined from this phase difference and, from this direction of rotation and from the direction of movement of the vehicle ( 3 ), the location of the right or left position of the wheel ( 2 ) is deduced.

The invention relates to a method and a device for locating the right orleft position of a wheel of a vehicle. It extends to a magneticmeasuring component suitable for incorporation in an electronicmonitoring system unit of a vehicle.

Increasingly, motor vehicles have, for safety purposes, monitoringsystems comprising sensors fitted on each of the wheels of the vehicle,dedicated to measuring parameters, such as the pressure or temperatureof the tyres fitted on these wheels, and intended to inform the driverof any abnormal variation of the measured parameter. These monitoringsystems are conventionally provided with an electronic unit fitted oneach wheel of the vehicle and incorporating a sensor comprising amicroprocessor and a radiofrequency transmitter (or RF transmitter), anda central unit for receiving the signals transmitted by thetransmitters, comprising a computer incorporating a radiofrequencyreceiver (or RF receiver) connected to an antenna.

One of the problems that monitoring systems have to resolve lies in theneed to have associated with each signal received by the receiver of thecentral unit, information concerning the location of the sensor andtherefore the wheel originating this signal, this obligation remainingthroughout the life of the vehicle, that is, having to be respected evenafter wheel changes or more simply reversals of the positions of thesewheels.

At the present time, a first locating method consists in using threelow-frequency antennas, each positioned near to one of the wheels of thevehicle, and performing a locating procedure that consists insuccessively exciting each of these three antennas by the transmissionof a low-frequency magnetic field.

According to this procedure, the sensor fitted on the wheel locatedclose to the excited antenna orders, in response and to the centralunit, the transmission of a low-frequency signal including anidentification code of said sensor, so that the successive excitation ofthe three antennas results in the locating of the three sensors fittedon the wheels adjacent to these antennas, and by deduction, the locationof the fourth sensor.

The main advantage of such a method lies in the fact that the locatingprocedure is very rapid and results in an almost instantaneous locatingafter the vehicle has started up.

However, this solution entails fitting the vehicle with three antennaswith all the attendant constraints: connecting cables, controlamplifiers, and so on, such that it is costly.

In order to limit the cost required by the locating procedure, a secondsolution currently implemented consists, firstly, in reducing the numberof antennas to two, and in positioning these two antennas close to thetwo front wheels, so as to enable said two front wheels to be located,and to differentiate the latter from the two rear wheels.

This second solution further combines, with the use of the two antennas,a technique based on a statistical method consisting in comparing theaccelerations of the wheels when turning, to provide a discriminationbetween the left wheels and the right wheels.

Because an antenna has been eliminated, this second solution is, asmentioned above, less costly than that described previously. However,this saving is obtained at the cost of the speed of the locatingprocedure which, according to this second solution, is relativelylengthy because of the fact that a consequential running time isrequired to obtain the left/right discrimination.

The present invention aims to overcome the drawback associated with thelength of the left/right locating procedure of the second techniquedescribed above, and its main objective is to provide a left/rightlocating method that is very efficient in terms of responsiveness, alsorequiring, for its implementation, a component with an overall price andinstallation cost less than the overall price of an antenna. Thiscomponent also needs to be small.

To this end, the first aim of the invention is a method of locating theleft or right position of a wheel of a vehicle equipped with anelectronic monitoring system unit, in which:

-   -   a magnetic measuring component is incorporated in the electronic        unit, comprising a core made of ferromagnetic material on which        are wound crosswise two windings configured to present maximum        sensitivity axes offset from each other by a predetermined angle        θ, and to position said magnetic measuring component in said        electronic unit so that the maximum sensitivity axes of the        windings extend in a plane intersecting the axis of rotation of        the wheel,    -   and, when the vehicle moves in a given direction of movement:        -   a signal generated by the variation of a magnetic field at            the terminals of each of the windings is measured, so as to            deliver two periodic signals phase-shifted from each other            by an angular value equal to (+or −) θ, each representative            of the variations of the values of the magnetic field            detected by said windings during a wheel rotation,        -   from this phase shift, the direction of rotation of the            wheel is determined,        -   and, from this direction of rotation and from the direction            of movement of the vehicle, the location of the right or            left position of the wheel is deduced.

The principle on which the invention is based was therefore to equipeach wheel to be located of a vehicle with a coil with two windings(each winding being used as magnetic sensors), positioned in such a waythat the signals at the terminals of said windings are phase-shiftedrelative to each other, and to deduce from this phase shift thedirection of rotation and the right/left location of the wheel.

According to this principle, the invention results in a very rapidlocating of the right/left position of a wheel, obtained, in practice,after a few wheel rotations.

Furthermore, according to the invention, the two windings (forming themagnetic sensors) are combined in one and the same component comprisinga single core around which the two windings are placed, and whose smalldimensions make it possible to incorporate it directly in a conventionalelectronic unit.

Because of this, the invention provides a solution with an overall price(cost and installation) that is significantly less than that of thesolutions requiring antennas. Furthermore, by combining two windingsaround one and the same ferrite core, a component is produced thatpresents two functions (magnetic sensors on two distinct axes) and witha minimal footprint. The space available for this type of component isin fact taken into account.

In order to obtain two signals that can easily be discriminated, andaccording to an advantageous embodiment of the invention, the magneticmeasuring component is positioned in the magnetic unit so that themaximum sensitivity axes of the windings extend in a plane orthogonal tothe axis of rotation of the wheel.

For the same purpose, and advantageously according to the invention, amagnetic measuring component is used that is provided with a core havingtwo pairs of parallel faces around each of which is placed a winding,configured so that said pairs of parallel faces are orthogonal to eachother.

In order to increase the sensitivity and therefore the reliability ofthe method according to the invention, the vehicle is, moreover,advantageously equipped with a magnet that is fixed relative to eachwheel equipped with a magnetic measuring component, said magnet beingpositioned and presenting a power suitable for generating a magneticfield covering a zone passed through by the windings when said wheelrotates.

The invention extends to a device for locating the right or leftposition of a vehicle wheel equipped with an electronic monitoringsystem unit. According to the invention, this locating device comprises,incorporated in each electronic unit:

-   -   a magnetic measuring component comprising a core made of        ferromagnetic material on which are wound, crosswise, two        windings formed so as to present maximum sensitivity axes offset        from each other by a predetermined angle θ, said magnetic        measuring component being positioned in said electronic unit so        that the maximum sensitivity axis of each winding extends in a        plane intersecting the axis of rotation of the wheel,    -   means of measuring a signal at the terminals of each of the        windings, able to deliver two periodic signals phase-shifted        from each other by an angular value equal to (+or −) θ, each        representative of the variations of the values of the magnetic        field detected by said windings during a wheel rotation,    -   and a computation unit programmed to determine, from the phase        shift between the two periodic signals, the direction of        rotation of the wheel, and to deduce, from this direction of        rotation and from the direction of movement of the vehicle, the        location of the right or left position of the wheel.

Advantageously according to the invention, the magnetic measuringcomponent is positioned in the magnetic unit so that the maximumsensitivity axes of the windings extend in a plane orthogonal to theaxis of rotation of the wheel.

Furthermore, this magnetic measuring component is advantageouslyprovided with a core having two pairs of parallel faces around each ofwhich is wound a winding, configured so that said pairs of parallelfaces are orthogonal to each other.

The locating device according to the invention also, advantageously,comprises a magnet mounted in a fixed manner on the vehicle relative toeach wheel equipped with a magnetic measuring component, said magnetbeing positioned and presenting a power suitable for generating amagnetic field covering a zone passed through by the windings when saidwheel rotates.

The invention also covers, as an element essential to implementing thelocating method according to said invention, a magnetic measuringcomponent suitable for incorporation in an electronic monitoring systemunit of a vehicle, comprising a core made of ferromagnetic material onwhich are wound crosswise two windings formed so as to present maximumsensitivity axes offset relative to each other by a predetermined angleθ.

Furthermore, the core of this magnetic measuring componentadvantageously has two pairs of parallel faces around each of which ispositioned a winding, configured so that said pairs of parallel facesare orthogonal to each other.

Advantageously, this magnetic measuring component is thus, for example,provided with a rectangular, parallelepipedal core.

Other characteristics, aims and advantages of the invention will becomeapparent from the detailed description that follows, given withreference to the appended drawings, which represent, by way ofnonlimiting example, a preferred embodiment. In these drawings:

FIG. 1 is a partial and diagrammatic perspective view of a vehicleequipped with a locating device according to the invention,

FIG. 2 is a diagrammatic perspective view of a magnetic measuringcomponent of a locating device according to the invention,

FIG. 3 is a functional block diagram of the processing electronics ofthis locating device,

and FIGS. 4 a and 4 b are two diagrams illustrating the principle of thelocating method implemented according to the invention.

The locating device according to the invention represented by way ofexample in FIG. 1 is intended to locate the right or left position of awheel of a vehicle.

This locating device is more specifically intended to be installed onvehicles provided with a monitoring system comprising electronic units 1mounted on each of the wheels 2 of vehicles 3, incorporating sensorsdedicated to measuring parameters, such as pressure and/or temperatureof the tires fitted on these wheels 2, and intended to inform the driverof any abnormal variation of the measured parameter.

This locating device firstly comprises a magnetic measuring component 4suitable for incorporation in an electronic unit 1, comprising twowindings 8, 9 arranged so that their respective maximum sensitivity axesS8, S9 extend in a plane perpendicular to the axis of rotation (R) ofthe wheel 2, and are offset from each other by a predetermined angleθ=90°.

To this end, and as represented in FIG. 2, this magnetic measuringcomponent 4 comprises a cube-shaped ferrite core 5 provided, on each ofthe four parallel edges, with strips such as 6, 7 projecting relative tosaid edges so as to extend edgewise and projecting from four faces ofsaid cubic core: a first pair of two opposing parallel faces such as 5a, and a second pair of two opposing parallel faces such as 5 b.

Furthermore, the first winding 8 is formed around the first pair ofparallel faces 5 a, whereas the second winding 9 is formed around thesecond pair of parallel faces 5 b.

Arranged in this way, when the wheel 2 rotates, each of these windings8, 9 presents, between its two terminals, a potential difference thatvaries according to a sinusoidal function of a period equal to theperiod of rotation of said wheel.

It should be noted that, in the example represented, the two windings 8,9 are independent of each other. As a variant, these windings could bedependent. It is sufficient in practice to be able to measure a variablepotential difference at the terminals of each of them.

A winding 8, 9 mounted on a wheel 2 of a vehicle 3 detects, in practice,the overall magnetic field prevailing around this winding, consisting ofthe Earth's magnetic field added to the environmental magnetic fieldthat can in particular result from the presence of electrical ormagnetic equipment on board the vehicle or present outside the vehicle(high-voltage line, for example).

Now, when the wheel 2 rotates, each winding 8, 9 is moved along acircular path, such that this winding 8, 9 detects a variable magneticfield and that the potential difference measured at the terminals of thewinding presents corresponding cyclical variations.

Furthermore, since the two windings 8, 9 are positioned, according tothe invention, so that their maximum sensitivity axes S8, S9 areorthogonal, the signals representative of the potential difference atthe terminals of said windings are phase-shifted relative to each otherby an angle equal to (+or −) 90°, such that, as represented in FIGS. 4 aand 4 b, the analysis of this phase shift makes it possible to determinethe direction of rotation of the wheel 2.

In order to measure and process the potential difference at theterminals of each winding 8, 9, the device according to the inventionfirstly comprises an amplification module 10 and a shaping module 11incorporating a comparator, such that, when the wheel 2 rotates:

-   -   the signal at the terminals of each winding 8, 9 is a very low        amplitude sinusoidal signal,    -   the signal at the output of the amplification module 10 is a        sinusoidal signal of the same period as the preceding signal but        with an amplitude greater than that of said signal,    -   and the signal at the output of the shaping module 11 is a        square signal of the same period as the sinusoidal signals.

The device according to the invention further comprises a computationunit 12 to which the shaped signal is delivered, programmed to:

-   -   determine, as mentioned above, from the analysis of the phase        shift between the two sinusoidal signals, the direction of        rotation of the wheel 2,    -   and deduce from this direction of rotation and from the        direction of movement of the vehicle 3, determined elsewhere by        any method known per se, the right or left position of the wheel        2.

Lastly, and according to the invention, the vehicle 3 can also comprise,as represented in FIG. 1, permanent magnets or electromagnets 13 fixedon the bodywork level with the wheel arches 14, such that the magneticfield created by each of these magnets 13 is detected by the windings 8,9 mounted on the corresponding wheel 2, increasing the overall magneticfield detected by the windings, and consequently the amplitude of thesinusoidal signals at the output of the amplification module 10.

The device according to the invention described above therefore makes itpossible, by incorporating a simple magnetic measuring component 4 ofsmall dimensions and with a low purchase cost and which is easy toinstall in each electronic unit 1 fitted on a wheel 2 of a vehicle 3, tovery rapidly locate, after a few rotations of the wheel 2, the right orleft position of said wheel.

1. A method of locating the right or left position of a wheel (2) of avehicle (3) equipped with an electronic monitoring system unit (1),characterized in that it consists: in incorporating in the electronicunit (1) a magnetic measuring component (4) comprising a core (5) madeof ferromagnetic material on which are arranged, crosswise, two windings(8, 9) configured to present maximum sensitivity axes (S8, S9) offsetfrom each other by a predetermined angle θ, and in positioning saidmagnetic measuring component in said electronic unit so that the maximumsensitivity axes (S8, S9) of the windings (8, 9) extend in a planeintersecting the axis of rotation (R) of the wheel (2), and, when thevehicle moves in a given direction of movement: in measuring a signalgenerated by the variation of a magnetic field at the terminals of eachof the windings (8, 9), so as to deliver two periodic signalsphase-shifted from each other by an angular value equal to (+or −) θ,each representative of the variations of the values of the magneticfield detected by said windings during a wheel rotation (2), indetermining from this phase shift the direction of rotation of the wheel(2), and in deducing, from this direction of rotation and from thedirection of movement of the vehicle (3), the location of the right orleft position of the wheel (2).
 2. A device for locating the right orleft position of a wheel (2) of a vehicle (3) equipped with anelectronic monitoring system unit (1), characterized in that itcomprises, incorporated in said electronic unit: a magnetic measuringcomponent (4) comprising a core (5) made of ferromagnetic material onwhich are arranged, crosswise, two windings (8, 9) formed so as topresent maximum sensitivity axes (S8, S9) offset from each other by apredetermined angle θ, said magnetic measuring component beingpositioned in said electronic unit so that the maximum sensitivity axes(S8, S9) of the windings (8, 9) extend in a plane intersecting the axisof rotation (R) of the wheel (2), means (10, 11) of measuring a signalat the terminals of each of the windings (8, 9), able to deliver twoperiodic signals phase-shifted from each other by an angular value equalto (+or −) θ, each representative of the variations of the values of themagnetic field detected by said windings during a wheel rotation (2),and a computation unit (12) programmed to determine, from the phaseshift between the two periodic signals, the direction of rotation of thewheel (2), and to deduce, from this direction of rotation and from thedirection of movement of the vehicle (3), the location of the right orleft position of the wheel (2).
 3. The locating device as claimed inclaim 2, characterized in that the magnetic measuring component (4) ispositioned in the magnetic unit (1) so that the maximum sensitivity axes(S8, S9) of the windings (8, 9) extend in a plane orthogonal to the axisof rotation (R) of the wheel (2).
 4. The locating device as claimed inclaim 3, characterized in that the magnetic measuring component (4) isprovided with a core (5) having two pairs of parallel faces (5 a, 5 b)around each of which is wound a winding (8, 9), configured so that saidpairs of parallel faces are orthogonal to each other.
 5. The locatingdevice as claimed in claim 2, characterized in that it comprises amagnet (10) mounted in a fixed manner on the vehicle (3) relative toeach wheel (2) equipped with a magnetic measuring component (4), saidmagnet being positioned and presenting a power suitable for generating amagnetic field covering a zone passed through by the windings (8, 9)when said wheel rotates.
 6. The locating device as claimed in claim 3,characterized in that it comprises a magnet (10) mounted in a fixedmanner on the vehicle (3) relative to each wheel (2) equipped with amagnetic measuring component (4), said magnet being positioned andpresenting a power suitable for generating a magnetic field covering azone passed through by the windings (8, 9) when said wheel rotates. 7.The locating device as claimed in claim 4, characterized in that itcomprises a magnet (10) mounted in a fixed manner on the vehicle (3)relative to each wheel (2) equipped with a magnetic measuring component(4), said magnet being positioned and presenting a power suitable forgenerating a magnetic field covering a zone passed through by thewindings (8, 9) when said wheel rotates.